Context. Fault correction process is one of the two main activities in software evolution model. As it is very important for software maintainability, software industry especially large-scaled global companies, aim to have mature fault correction processes that detect faults and correct them in a continuous and efficient way. Considerable amount of effort is needed and some measures should be taken in order to be successful. This master thesis is mainly related with fault correction and finding possible solutions for better process. Objectives. The main aim of this study is to investigate and identify influential factors having affects over undesired fault correction outcomes. This study has three main stages: 1) to identify factors from company data that have affects over target factors, 2) to elicit influential factors from interviews and literature review, 3) to prioritize influential factors based on their significance. Based on the outcomes, giving recommendations to company and software industry is the other aim of this master thesis. Methods. This study mainly reflects the empirical research of software fault correction process and undesired outcomes of it. In this master thesis, both quantitative and qualitative data analysis were performed. Case study was conducted with Ericsson AB that data analysis was made with the archival data by using several methods including Machine Learning and Apriori. Also, surveys and semi-structured interviews were used for data collection instruments. Apart from this, literature review was performed in order to collect influential factors for fault correction process. Prioritization of the influential factors was made by using hierarchical cumulative voting. Results. Throughout the case study, quantitative data analysis, interviews and literature review was conducted and totally 45 influential factors were identified. By using these factors prioritization was performed with 26 practitioners (4 internal and 22 external) in order to find which factors are most a) significant and b) relevant in undesired fault correction outcomes. Based on the outcomes of prioritization, cause-effect diagram was drawn which includes all the important factors. Conclusions. This research showed that there are lots of factors influencing fault correction process. The practitioners mostly complained about the lack of analysis of deeply including correction of faults are not resulted the new requirements and they are not used for process improvement. Also, limited resources (such as work force, vacations and sickness), unbalanced fault correction task assignment and too much fault reports at the same time cause problems. Moreover, priorities of faults and customers affect the lead time of fault correction process as the critical faults are fixed at first. / +90 533 7698780